Generally, magnetic recording media such as magnetic tapes are prepared by coating a magnetic paint comprising magnetic powder and binder resin on a support. Since the conventional types of magnetic recording media comprise only one magnetic layer, it is required to cover a wide frequency bandwidth from the low to the high with single kind of magnetic powder. Particularly in the recent tendency of making recording densities higher, there are the demands for magnetic recording media improved to have the recording characteristics in the high band and low noises. Therefore, magnetic powder having both of high coersive force, Hc and large surface area represented by BET values are used.
However, since the magnetic recording media are each comprised of a single kind of magnetic powder, i.e., a single kind of magnetic layer, these media have to use high Hc and BET magnetic powder in the excess of paying attention to improve the characteristics of the high bandwidth, thereby lowering the characteristics of the low bandwidth.
On one hand, in the magnetic recording media for video use, there have been some proposals for the media each having a plurality of magnetic layers so as to increase the magnetic recording capacity or to improve and/or keep the balance of the magnetic recording characteristics between the high and low band each of the media. For further details, refer to Japanese Patent Publication Open to Public Inspection (hereinafter referred to as Japanese Patent O.P.I. Publication) Nos. 48-98803/1973 and 59-172142/1984, Japanese Patent Examined Publication No. 32-2218/1957, Japanese Patent O.P.I. Publication No. 51-64901/1976, Japanese Patent Examined Publication No. 56-12937/1981, and Japanese Patent O.P.I. Publication Nos. 58-56228/1983 and 63-146211/1988.
According to the above-given prior arts, the magnetic layers are so designed as to separate the characteristic functions thereof into two; namely, the upper layer for taking the role of video outputs, and the lower layer for taking the roles of chroma and audio outputs. Further, in the media having the multilayered or laminated type magnetic layers, the uppermost magnetic layer is generally so formed as to have a thin layer thickness of not more than 0.6 .mu.m.
On the other hand, the surface of the above-described uppermost layer is finished to be so flat and smooth as to increase the output, particularly a video output, of the high frequency band. However, such a flat and smooth surface is liable to produce a reeling failure when taking up or rewinding up a medium or especially a tape, a running failure or a output disorder. To remedy these disadvantages, it may be considered to provide a backing layer comprising non-magnetic particles set with binders to the surface of a support on the opposite side of a magnetic layer.
However, when a magnetic recording medium is taken up, the unevenness of the backing layer surface is imprinted onto the uppermost magnetic layer surface so as to damage the surface characteristics, thereby seriously deteriorating the electromagnetic conversion characteristics of, especially, video outputs of the medium. It may be presumed that the unevenness of the backing layer surface is liable to be imprinted onto the magnetic layer surface, because the backing layer surface is so made coarse as to secure the running property thereof. According to the studies on the invention, the reasons thereof are that the RF output of the magnetic layer is seriously deteriorated by the transfer when the backing layer surface is uniformly roughened and, in particular, the characteristics, i.e., the video output or RF output, of the magnetic layer are seriously affected when the imprint is received from the backing layer, because the uppermost magnetic layer is a thin layer having a thickness of not more than 0.6 .mu.m. The above-mentioned disadvantages will lead a medium comprising only a single magnetic layer to an unexpected characteristic deterioration.